1. Field of the Invention
This invention relates to devices for external fixation of fractured bones, and, more particularly, to an external fixator in which bone setting pins are clamped from a plurality of angles for fixation of multiple fragments of an end portion of a radius bone.
2. Description of the Related Art
The fracture of the distal radius is one of the most common human fractures, occurring in as many as 350,000 people per year in the United States alone. The conventional processes both for reducing such a fracture and for maintaining the bones in proper alignment during the subsequent healing process involves applying and maintaining an extension force across the fracture, with ligamental taxis being relied upon to hold the bones in place. The process for treating a fractured distal radius is described in the 1901 edition of Gray's Anatomy in the following manner, “The treatment consists of flexing the forearm, and making a powerful extension from the wrist and elbow, depressing at the same time the radial side of the hand, and retaining the parts in that position by well-padded pistol-shaped splints.”
A common method for the treatment of a fractured distal radius involves the use of standard immobilizing cast techniques, preventing movement of the radiocarpal joint throughout the course of rehabilitation. A problem with this method is that it sometimes results in inadequate internal fixation, which can cause deformity, pain, and prolonged disability.
Another method for treating a fractured distal radius involves external pin fixation. This process involves the surgical insertion of skeletal traction pins on both sides of the fracture, with a frame being connected to the pins for immobilizing the bones, and for holding them together until the fracture is mended. Initial structures and methods for applying external pin fixation for the treatment of a fractured distal radius provide for the immobilization of the radiocarpal joint, so that the hand cannot be flexed. While this type of fixation often provides an improvement over conventional casting techniques in the management of severe fractures of the distal radius, immobilization of the radiocarpal joint during the treatment period typically results in a long period of stiffness and disability after the external fixation device is removed. Typically, the external fixation device is left in place during the healing process for six to eight weeks. After the fixation device is removed, three to six months are required for the patient to regain motion of his hand.
Subsequent structures and methods have been developed to provide adequate fixation during the healing process while allowing flexure in the radiocarpal joint. Using these newer structures and methods, patients have been able to gain immediate use of the joint after surgery.
An example of a fixation device and fixation method that provides adequate fixation and allows flexure in the radiocarpal joint is described in U.S. Pat. No. 6,585,736, the disclosure of which is incorporated herein by reference. U.S. Pat. No. 6,585,736, describes a fixation device that is configured to provide external fixation of a fractured distal radius by including a first number of holes for pins extending downward from the fixture into one or more bone fragments, rods that extend downward and hold pins laterally into one or more bone fragments, and a second number of holes for pins extending downward from the fixture into the shank of the radius. The fixture also includes a sliding block through which rods extend to hold pins directed laterally into the fragments. A sliding plate including a number of holes aligned with the first number of holes is moved by a pair of setscrews to clamp the pins extending through the first number of holes. The second number of holes includes a hole within a sliding structure allowing a single pin to be moved with a fixture to provide extension between the fragments and the shank of the radius.
What is needed is a simpler and more functionally effective structure and method for holding pins laterally into bone fragments. Since a plurality of individual rods have typically been used to secure fragments laterally, what is needed is a structure and method that will provide a more reinforced structure to hold the pins laterally. In addition, such a structure and method would preferably allow the laterally placed pins to be placed at a plurality of angles. Such a structure and method would still allow mobility of the hand and wrist while presenting fewer surfaces to get caught on other objects and being more cost effective due to it having fewer parts.